Organic and inorganic components of saliva Flashcards
What are the role of salivary mucins?
- Lubrication of hard and soft tissues to avoid harm from mechanical damage
- Bacterial agglutination
- Direction of bacterial colonisation
- Barrier to demineralisation and microbial colonisation
- Antimicrobial and anti fungal activity
- Regulates other salivary proteins
- Protects against dessication (drying out of the mouth)
What is the role of statherin and salivary proline rich proteins?
- Inhibition of HAP growth
- Control of mineral deposition and growth
What linked sugars do salivary mucins contain?
O- and N- linked sugars
What is the common core structure all N-linked oligosaccharides contain?
Three mannose and two N-acetylglucosamine residues
What does a mucin monomer contain?
- Oligosaccharide
- Cysteine residue
- Repeat structure
What are the two types of salivary mucin?
MG1 and MG2
How many different gene products is MG1 a mixture of?
3
How many different gene products is MG2 a mixture of?
1
Is MG1 an oligomeric structure or monomeric?
Oligomeric
Is MG2 an oligomeric or monomeric structure?
Monomeric
What does MG1 form complexes with?
Amylase, PRP’s, histatines, statherin and antimicrobial peptides
What does MG2 bind to?
Oral pathogens and yeast (candida)
Properties of statherin?
High proline content, small, high negative charge, produced by acinar cells, binds to HAP via two possible sites.
What are the functions of statherin?
Inhibits crystal growth and precipitation of hydroxyapatite
What are properties of proline rich proteins?
Rich in proline, high proportion in total saliva, high negative charge, strongly absorbed to HAP.
What are functions of PRP’s?
- Inhibition of HAP growth
- Interact with oral micro-organisms (-NH2 terminal binds COOH terminal interacts with bacterial cell walls)
- Highly selective - exclusion of pathogens
What are properties of histatins?
- Rich in histidine
- Basic character due to presence of Arg and Lys
- Bind to HAP
- Small
- Highly conserved
Functions of histatins
Potent inhibitor of candida
Buffer?
What are the three types of immunoglobulins in saliva and GCF?
IgA, IgM and IgG
What are functions of histatins?
- Bacterial agglutination
- Specific Ab-Ag targeting against bacterial adhesins
What does amylase do?
Catalyses hydrolytic cleavage of a 1-4 glycosidic linkages. Depends on calcium ions and is chloride activated.
Functions of amylase?
CHO digestion (aldehyde)
Interactions with oral micro-organisms
Present in carious lesions
Present in tears
What are the properties of lysozymes?
- Originates from striated duct
- Hydrolyses a 1-4 linkages between N-acetylmuramic acid and N-acetylglucosamine in bacterial cell walls
- May co-operate with SlgA (immunoglobulin A)
- Binds to HAP
What are the functions of lysozymes?
Bacterial cell wall lysis - antimicrobial
What does salivary peroxidases do?
- Catalyses conversion of peroxide (from bacterial metabolism) and thiocyanate into hydrothiocyanite
- Important detoxifier - must remove H2O2 to prevent free radical formation, may have a role in perio disease
What does lactoferrin do?
Has an antibacterial function, binds Fe 3+ (essential bacterial nutrient)
What are cystatins?
Small proteins which are ubiquitous throughout all bodily fluids, binds to HAP
What are the functions of cystatins?
Inhibitors of cysteine proteases and protection against acid erosion.
What are two examples of pH rise factors?
Urea and slain, these are metabolised to produce ammonia to increase pH and produce putrescine (halitosis)
Why are hydrogen ions related to pH?
- Their concentration determines the pH of the oral environment
Why does the pH of saliva vary?
According to flow rate (higher flow rate = higher pH
Why is pH important in the mouth?
- Maintains ionic product for hydroxyapatite
- Isoelectric point for salivary protein precipitation on to tooth surfaces
- Optimal pH for salivary enzymes
What do higher flow rates of saliva increase?
Salivary buffering
What are the MOST important ions in salivary buffering?
Bicarbonate
Where are bicarbonate ions produced?
Striated epithelium of the secretory ducts and parotid gland
What does bicarbonate ion concentrations increase with?
Increased metabolic activity of salivary glands
What is the counter ion for bicarbonate?
Sodium
What is the counter ion for phosphate?
Phosphate
Do sodium ions increase when flow rate increases?
Yes
Do potassium ions increase when flow rate increases?
Stays the same
What are the possible origins of magnesium ions?
Cellular degradation
Early carious attack
Do magnesium ions increase or decrease with an increased flow rate?
Decrease
What do calcium ions do in the mouth?
- Form complexes with calcium binding salivary proteins
- Important role in maintenance of ionic product for hydroxyapatite
Do calcium ions increase with increased flow rate?
Stay the same
What do phosphate ions do?
- Act as a buffer, especially in unstimulated saliva
- Important in maintenance of ionic product for hydroxyapatite
Do phosphate ions increase with increased salivary flow?
Decrease
What is the formula of hydroxyapatite?
Ca10(Po4)6(OH)2
